What is the lewis structure for NBr3? How many electron pairs in the central atom of NBr3? How many bonding electrons pairs of the central atom of NBr3? How many non-bonding pairs of the central atom of NBr3? What is the molecular geometry of NBr3?
The Correct Answer and Explanation is :
The Lewis structure for nitrogen tribromide (NBr₃) can be represented as follows:
- Count the valence electrons: Nitrogen (N) has 5 valence electrons, and each bromine (Br) has 7 valence electrons. Thus, the total number of valence electrons for NBr₃ is:
[
5 \text{ (from N)} + 3 \times 7 \text{ (from Br)} = 5 + 21 = 26 \text{ valence electrons}
] - Draw the skeletal structure: Place nitrogen as the central atom, surrounded by three bromine atoms. Connect each Br atom to N with a single bond.
- Distribute remaining electrons: Each bond consists of 2 electrons, using 6 electrons for the three N-Br bonds, leaving us with 20 electrons. These are placed as lone pairs on the Br atoms. Each Br will receive 6 electrons (3 lone pairs) to complete its octet, utilizing 18 of the remaining electrons, leaving 2 electrons.
- Place remaining electrons on the nitrogen: Since nitrogen can only accommodate a maximum of 8 electrons in its valence shell, these 2 electrons are added as a lone pair on the nitrogen atom.
Summary of Electron Pair Counts in NBr₃:
- Total electron pairs around N: 4 pairs (1 lone pair and 3 bonding pairs).
- Bonding electron pairs: 3 pairs (from N-Br bonds).
- Non-bonding electron pairs: 1 pair (the lone pair on N).
Molecular Geometry:
The molecular geometry of NBr₃ is trigonal pyramidal. This shape arises because the presence of the lone pair on nitrogen repels the bonding pairs, resulting in a three-dimensional structure where the bromine atoms occupy the base of a pyramid and the nitrogen atom is at the apex.
Explanation:
The Lewis structure illustrates the distribution of electrons in a molecule. In NBr₃, nitrogen serves as the central atom, forming three covalent bonds with bromine atoms. The lone pair of electrons on nitrogen contributes to the molecule’s polarity and affects the geometry. The trigonal pyramidal shape is a consequence of the VSEPR (Valence Shell Electron Pair Repulsion) theory, which states that electron pairs around a central atom will arrange themselves to minimize repulsion, resulting in specific molecular shapes. The molecular geometry impacts the physical and chemical properties of the substance, such as its polarity and reactivity.